1. Field of the Invention
The disclosure relates to an optical fiber multi-wavelength filter and a method of controlling a wavelength of an output spectrum of the filter, and more particularly, to an optical fiber multi-wavelength filter based on a polarization-diversity loop configuration capable of tuning a wavelength of an output spectrum and a method of controlling a wavelength of an output spectrum of the filter.
2. Description of the Related Art
In an optical communication system, multi-wavelength light sources or all-fiber wavelength-selective filters have received much attention as main components to meet the increased bandwidth demands.
Among these components, an optical fiber filter is used as a core component for wavelength routing in a wavelength-division-multiplexing network.
In the optical fiber filter, it is important to accurately adjust the position of an absolute wavelength by an ITU-grid standard wavelength in the wavelength-division-multiplexing network while maintaining the wavelength spacing of the filter.
In particular, the optical fiber multi-wavelength filter has been heavily researched because the filter is easy to design and use.
To control an absolute channel wavelength of the optical fiber multi-wavelength filter, a mechanical method and a polarization control method have been proposed.
For an optical fiber multi-wavelength filter that forms an interference spectrum using a polarization-maintaining fiber, wavelength tuning of the filter channel has been accomplished by the mechanical method of applying strain to the polarization-maintaining fiber to change the birefringence, or by the polarization control method of adjusting a phase difference between principal polarization components.
However, the mechanical method may deteriorate the durability of the polarization-maintaining fiber over repeated operations.
Also, the polarization control method has a disadvantage of being inapplicable to wavelength tuning in a higher-order filter having sharper edge and flatter passband.